The computerized system, in use since 2004, has succeeded in preventing trains from crashing into each other or into barriers at the end of the line. But according to MTA administrator Paul J. Wiedefeld, its hair-trigger response to slippage on the tracks has resulted in hard, sudden stops that can flatten the metal surface of the wheels - putting them in added danger of cracking.
Wiedefeld said the MTA has paid more attention to the issue of wheel damage since the discovery last spring of a crack in one of the wheels of a car in a rail yard.
That discovery prompted the agency to inspect wheels much more frequently than the 45-day schedule recommended by the manufacturer. That led to service disruptions, including severe crowding and long waits at platforms.
Last week, as train slippage caused by leaves sent a growing number of cars to the shop, the MTA announced that it would terminate its northern service at Timonium, using buses to serve stations between there and Hunt Valley. But by the weekend, the MTA had so many cars out of service that it decided to call an emergency halt to service north of North Avenue - the most leafy section.
Wiedefeld said the agency is attempting to find an interim solution to the problems by recalibrating the train protection system so that it acts more like the anti-lock brake systems found on cars. The "ultimate fix," he said, will not come until the MTA completes its planned midlife overhaul of its train cars - a project expected to be finished about 2011-2012.
Until then, Wiedefeld said, the MTA has its maintenance shop working around the clock to repair or replace wheels. He said the flattened wheels can be fixed three times before they require replacement - a procedure that can put an entire car out of commission for 15 days.
Wiedefeld said he does not have an estimate now of how long it will take to fix the computer problem. He said any proposed solution would have to be tested on the main line and then verified by an independent contractor before it can be implemented. He added, however, that he doesn't think the disruptions will persist for months.
Porcari echoed Wiedefeld's reluctance to be pinned down to a target date for the return of full service, noting that the weather could be a factor in how long the disruptions continue.
